I'm not sure about Babylon 5, but I believe TNG was shot on film, but the effects were all done at broadcast resolution due to cost. This meant that when they released the DVD version, it was not difficult to create HD versions of all the "real" footage, but the effects were all in standard definition, so they looked awful. For the Blu-ray remaster, I believe they redid all the effects with modern CG, so they no longer look like crap.